Jet augmentation arrangement



July 1, 1952 R. s. BOUTELLE 2,601,963

JET AUGMENTATION ARRANGEMENT Filed April 9, 1946 INVENTOR. 0rd 8. Boutelle IS PATENT ATTORNEY Patented July 1, 1952 2,601,963 j I JET AUGMENTATION ARRANGEMENT Richard S. Boutelle, Hagerstown,

Md., assignor to Fairchild Engine and Airplane Corporation, a corporation of Maryland Application April 9, 1946, Serial No. 660,659

13 Claims. 1 The present invention relates to power plants and more particularly to improved cooling and cowling means adapted for augmentation of the jet thrust developed by aircraft power plants.

This invention is directed toward increasing the jet efiect orthrust of the exhaust of an engine and augmenting the same by its cooperative action with the engine cooling air. The invention consists essentiallyof an arrangement in which the energy and velocity of the exhaust gases are utilized as they come directly from the engine, or as they maybe increased by rammed air admitted to the exhaust stacks or manifold. The improved arrangement contemplates a parallel or co-axial travelof the cooling air about the hot exhaust gas duct in such a manner that the cooling air rammed within the engine cowling is heated both by fthe engine and by its passage along the exhaust duct to increase its pressure at the point of discharge. The invention also is directed to thei mprove'dthrust effect resulting from the force imparted by the exhaust nozzle upon the larger mass of, slower moving engine cooling air, as well as to improved engine cooling conditions and the cooling of the exhaust gases tending to improve \fiame dampening;

It is accordingly a major object of this invention to augment the thrust of the power plant and propellerinstallation by utilization of the engine exhaust and the engine cooling air. A further object resides in an increased jet efiect obtained by imparting thrust to a larger volume of slower moving engine cooling air. It is a corollary purpose to provide for heating of the engine cooling air by the exhaust gases to increase pressure of this cooling air at its discharge point.

A further objective of this invention is to provide improved flame dampening and silencing by long travel of the exhaust gases, their cooling by the engine cooling air passing around the exhaust gas duct as well as by the admixture of rammed air therewith. It is also a purpose of the invention to increase the circulation and volume of engine cooling air by the suction effect of the jet exhaust to thereby improve the cooling of the engine. A further object resides in the provision of an installation in which internal regulation of the volume of the engine cooling air is facilitated and the aerodynamic characteristics of the installation thereby improved.

Other advantages and objects of the present invention will occur to those skilled in the art after an understanding of the present invention as hereinafter described and shown in the accompanying' drawings forming a part hereof, in which: r p p Fig. 1 is a perspective view of anaircraft power plant and propeller installation as supported from a wing and embodying a preferred form of this invention; Fig. 2 is a diagrammatic side of the power plant installation of Fig. 1;

Fig. 3 is a front view of the installation shown in Fig. 2;

Fig. 4 is a rear view of the same; and

, Fig. 5 is a detailed cross-section of an inlet to tion is equally applicable to engines of other types. The engine of exhaust stacks exhaust gases'from each engine cylinder communicate with the main rearwardly extending exhaust duct 20. I j I The naoelle or cowl I6 is preferably oval-shaped in cross-section extending in a streamline form from a point well forward of the wing leading edge rearwardly beyond the trailing edge of the wing beyond which it preferably terminates with -l 2 is. provided with a plurality a circular cross-section. The naoelle body lfiis provided at its forward portion with an inlet or mouth 22 into which cooling air is rammed by the forward movement ofthe aircraft, and the naoelle terminates in a. circular exit opening24.

at its trailing portion. The naoelle l 6 is provided with a series of former ringsf26, 28and 30' upon the forward one of which is mounted the engine fire-wall 32. The interior of the naoelle from the fire-wall 32 rearwardly is. divided,by a substantially horizontal partitioningplate 34 which ex-. tends across the width of the naoelle at or slightly above its mid-portion, sloping slightly upwardly to a point between the trailing edge of the wing and the naoelle exit 24. I V

The exhaust duct 20, in the preferred modification shown in the drawings, is provided with a rammed air inlet 36 facing into the nacelle inlet 22 and preferably provided with a spring check valve 38 as more particularly shown in Fig. 5. This check valve is preferably pivotally mounted at at, having an'upwardly extending lever portion 42 to which an adjustable tension spring 44 is attached and connected to a lug 46 on the top DI the exhaust duct. The springcheck'valveis elevational sectionor. tailpipes [8 by which thearranged in such manner that while the aircraft is at rest upon the ground, or being moved about at speeds below a predetermined magnitude, the rammed air forces acting upon the valve plate 38 are insufficient to overcome the tension of the spring 44 and under these conditions the valve remains closed in its lower dotted position causing the exhaust gases to be discharged rearwardly within the duct without dilution by rammed air. When the speed of the aircraft is increased above this predetermined level, as in flight, the rammed air forces acting upon the valve plate 38 are sufiicient to overcome the tension of the spring 44 and the valve is opened to its upper dotted position permitting cooling air to enter the exhaust duct 20.

A regulating valve 48 is preferably located within the nacelle aft. of the win trailing edge and forward of the nacelle exit 24 in the region of the trailing portion of the partition plate 34 which terminates in a vertical partition plate 59. The regulating valve 48 is preferably hinged at 52 and has pivotally connected to it an operating push-pull rod 54, the entire regulatin valve and actuating mechanism being enclosed within the nacelle body and other portions of the aircraft in communication with the pilot cockpit, or a suitable automatic control. The regulating baiiie 48 may be notched to fit around the exhaust duct 20 but need not fit tightly against the inner walls of the nacelle as, a small air passage therethrough is desirable at all times. The exhaust duct 28 is preferably increased in cross-section at the point at which the engine exhaust gases l8 open into it but rearwardly of the engine it is preferably reduced gradually in cross-section and bent upwardly to have its horizontal trailing portion discharge through an opening or nozzle 56 centrally or co-axially with the nacelle air exit 24. It is also preferable that the duct 20 extend centrally and co-axially with the nacelle for a substantial distance as shown in Fig. 2.

The operation of the present jet augmented power plant in flight is substantially as follows: Assuming that the aircraft is flown at a speed in excess of that at which the check valve is adjusted to operate, rammed air is taken into the inlet 22 of the nacelle IS, a portion of the air passing over the cooling fins of the cylinders of the engine [2 and a. portion entering the inlet opening 36 of the exhaust duct 20 past the open valve 38, As indicated by the arrows in Fig. the coolin air passing over the engine cylinders and rearwardly within the nacelle 16, as well as about the exhaust duct 20, is heated by the engine exhaust ases and thus has its pressure increased as it approaches the point of discharge at 24. The flow of engine cooling air may be suitably controlled, as indicated above by the internal regulator plate 48 and its actuating mechanism 54.

The rammed air which enters the inlet 36 of the duct 20 becomes thoroughly mixed with the exhaust gases entering the duct from the exhaust stacks l8, causing a secondary or more complete combustion of the unburned fuel in the exhaust to thereby increase, the exhaust gas pressures at the outlet 56 of the exhaust duct 20. This lot thrust of the exhaust is increased by the discharge of the larger mass of slower moving engine cooling air passing out through the annular exit space 24 around, the nozzle 56, through which the exhaust gases are discharged, thus creating an augmenting effect by imparting the thrust force of the exhaust gas to a larger volume of slower moving air. This supplementary column of rammed air which is heated by both the engine and the exhaust duct is thus appreciably increased in pressure at the point of discharge to add to the thrust effect imparted to it by the exhaust gas nozzle. As a result of thelong travel of the exhaust gases within the duct 2! as well as by the cooling effect of the engine cooling air passing rearwardly through the nacelle and around the exhaust duct, the present arrangement provides a greatl improved flame dampening as well as a silencing device.

The present arrangement also accomplishes an improved cooling of the engine in view of the increased circulation and volume of the engine cooling air as a result of the suction created by imparting some of the force of the exhaust gases to this coolin air column. In other words the jet thrust imparted by the exhaust nozzle 58 to the mass, of cooling air passing through the annular exit 24, in addition to the beneficial thrust obtained, also serves as-an eductor device inducing a greater volume of cooling air to enter the nacelle mouth 22 and flow over the cylinders of the engine. It will also be noted that among the further improved results obtained by the present jet arrangement, the overall aerodynamic resistance of the power plant installation is materially reduced by virtue of the internal regulation of the cooling air volume as compared with prior arrangements which have been externally exposed to the surrounding air stream. A modification of the present arrangement contemplates the omission of the inlet opening at 36 in the exhaust duct and the check valve 36 and in certain installations it may be desirable to insulate the nacelle interior.

Other forms and modifications of the present invention, both with respect to its general arrangement and the details of its respective parts, which will become obvious to those skilled in the art after an understanding of this. invention, are intended to fall within the scope and spirit thereof as more particularly set forth in the appended claims.

I claim:

1. An exhaust thrust augmenter for an aircraft power plant comprising an air-cooled engine, a streamlined nacelle enclosing said engine having a cooling air inlet opening at its forward portion and an air outlet opening at its trailing portion arranged to direct cooling air flow from said inlet to said engine, rearward through, said nacelle and, out through said outlet opening, an exhaust duct in communication with'the exhaust gases from said engine having a gradually diminishing cross-section terminating in a nozzle common with the said air cooling outlet of said nacelle, said exhaust duct hav ing an inlet opening common to the cooling air inlet opening of said nacelle arranged such that cooling air is admixed with said exhaust gases from said engine to improve the combustion thereof, valve means disposed in the said duct inlet opening arranged to close the said exhaust duct inlet at predetermined lower speeds of the aircraft, and a controllable valve for regulating the volume of engine cooling air through said nacelle outlet.

2. An aircraft power plant installation comprising an air-cooled engine, an elongated nacelle enclosing said engine, said nacelle having a rammed air inlet at its forward portion for engine cooling air and an engine, cooling air outlet at its trailing portion, and a single continuous duct in communication with theexhaust of said engine disposed within said nacelle having its forward end open at a point forward of said engine to receive a portion of the rammed air flowing into the said nacelle air inlet, said duct having a gradually diminishing cross-section terminating in an outlet centrally disposed in the nacelle cooling air outlet at the same transverse plane thereof arranged to impart I augmented velocity to said cooling air and increased thrust to said power plant installation.

3. An exhaust thrust augmenter for an aircraft power plant installation comprisingan air-cooled engine, an elongated nacelle enclosingsaid engine having a forward cooling air inlet opening and a rearward cooling air outlet opening, said nacelle being elongated such that its length is greater than three times its greatest transverse dimension, an exhaustduct in communication with said engine exhaust co-extensively disposed within said elongated nacelle, said exhaust duct having a cooling air inlet within said nacelle inlet forward of said engine, said exhaust duct having an exhaust nozzle centrally discharging to the atmosphere at the said nacelle outlet opening, said exhaust duct having a gradually diminishing cross-section as it extends rearwardly to its smallest diameter at said exhaust nozzle, the interior of said nacelle arranged to cause cooling air admitted to said nacelle air inlet to flow over the cylinders of said engine and rearwardly about the said exhaust duct and nozzle to create an augmenting effect by imparting the thrust force of the exhaust in said exhaust duct to the larger volume of slower moving surrounding engine cooling air passing rearwardly through said nacelle outlet, and valve means disposed within said nacelle externally of said exhaust nozzle for controlling the fiow of said cooling air through said nacelle outlet.

4. In an aircraft having an air-cooled engine, anda streamlined nacelle enclosing said engine, means for augmenting the thrust of said engine including an exhaust duct extending substantially the full fore-and-aft length of said nacelle, said duct being open at its forward terminal to receive rammed fresh air entering the mouth of said nacelle at a point forward of said engine, said duct provided adjacent its forward portion aft of said forward open extremity with connections to said engine for the flow of exhaust gases therefrom to said duct, said duct having agradually diminishing cross-section terminating in an open nozzle at its rear extremity centrally disposed within the outlet at the trailing portion of said nacelle, spring-biased valve means disposed within the forwardly openingextremity of said duct for automatically closing said forward extremity of said duct at materially reduced and zero forward speeds and a controllable valve means extending across the rear portion of said nacelle around said exhaust duct for controlling the cooling air flow across said engine and through said nacelle outlet.

5. In a propeller-driven aircraft having a wing,

6. tremity disposedwithin the inlet portion of said nacelle and extending longitudinally rearwardly with gradually diminishing cross-section in the rearward direction terminating in an open no'zzle at its rearward extremity substantially centrally disposed within the air exit opening at the trailing edge of saidnacelle, valve means disposed at the forward extremity of said exhaust duct automatically closable below predet'erminedforward velocities at which the rammed air effect is overcome and the forward extremity of-said exhaust duct is closed to said cooling air inlet, conduit means for the carrying of the exhaust gases from said engine downwardly into the forward portion of-saidexhaust' duct aft of said automatic valve means, "a transverse bulkhead disposed within the aft portion of said nacelle about the trailing portion of said exhaust duct, said transverse bulkhead having an opening therein for the passage of engine cooling air therethrough, and controllable valve means for said opening in said'transverse' bulkhead.

6. In aircraft, a power plant installation, in cludingan air cooled engine, a nacelle enclos ing said engine, said nacelle having a forward cooling air inlet and a rearward cooling air outlet, an engine exhaust duct substantially co-extensive with the length 'of said nacelle, said duct having an inlet forward of said enginewithin said nacelle forward air inlet and an outlet at said nacelle rearward air outlet, conduit means for conducting exhaust gases from said engine to said duct, automatic means disposed within said duct in theregion of the forward end thereof arranged to'close said duct inletin accordance with the cooling air flow-into said nacelle air inlet, valve means .dispose'dwithin the cooling air flow within the rearward portion of'said nacelle exteriorly of the exhaust duct, the said nacelle and exhaust duct being substantially coextensive in length such that they have common air inlets and common air outlets arranged to admit cooling air to said nacelle for cooling said engine and to said exhaust duct for admixture with saidexhaust, and to have the engine cooling airaccelerated at said common outlet-by said admixed engine exhaust to augment the thrust of said power plant installation.

7. An exhaust thrust .augmenter for an aircraft power plant comprising an air cooled engine; a nacelle enclosing said engine having a cooling air inlet opening at its forward portion andan air outlet'opening at its trailing portion, said nacelle arranged to direct cooling air flow from said inlet to said engine, thence rear wardly through said nacelle and outwardly through said outlet opening; an exhaustduct in communication with the exhaust gas ports of said engine having a gradually diminishing -'cross-sec'tion rearwardly terminating in a nozzle common with the said air outlet of said nacelle, said exhaustduct having an inlet opening common with the cooling air inlet opening of said nacelle arranged such that cooling air "is admixedwithin said duct with said exhaust gases from said engine; andvalve means disposed in the said. duct inlet opening arranged to close the said inlet of said exhaust duct at predetermined lower speeds of the aircraft.

8. An exhaust thrustaugmenter for an aircraft power plant comprising an air cooled engine; a nacelle enclosing said engine having a cooling air inlet openingv atits forward portion and an air outlet opening at its trailing portion, said nacelle arranged to direct cooling air flow from said inlet to said engine, thence rearwardly through said nacelle and outwardly through said outlet opening; a duct in communication with the exhaust gases from said engine having a gradually diminishing cross-section 'rearwardly terminating in a nozzle common with the said air outlet of said nacelle, said exhaust duct having an inlet opening common to the cooling air inlet opening of said nacelle arranged such that cooling air is admixed with said exhaust gases from said engine to improve the combustion thereof; and valve means disposed wihin said nacelle externally of said exhaust duct for regulating the volume of engine cooling air passing rearwardly through said nacelle.

9. An, aircraft power plant installation comprising an, air cooled engine, an elongated nacelle enclosing said engine, said nacelle having an air inlet at its forward portion for the entrance of cooling air to the interior of said nacelle, said nacelle having an outlet at its trailing portion, an elongated augmenter tube having its forward portion in communication with the exhaust gases from, said engine, said elongated augmenter tube extending continuously from the region of said engine in the forward portion of said nacelle rearwardly to and through said outlet at said nacelle trailing portion, and a forwardly directed opening associated with the forward portion of said augmenter tube arranged for the entrance of cooling air from said nacelle inlet into said elongated. augmenter tube for admixture with said engine exhaust gases therewithin and the discharge thereof from said elongated augmentertube into the airstream through said nacelle outlet.

10. An aircraft power plant installation com prising an air cooled engine, an elongated nacelle enclosing said engine, said nacelle having an airinlet at its forward portion for the entrance of cooling air to the interior of said nacelle, said nacelle having an outlet at its trailing portion, an elongated augmenter tube having its forward portion in communication with the exhaust gases of said engine, said elongated augmenter tube extending continuously rearwardly to and through said outlet at said nacelle trailing portion, a forwardly directed opening associated with the forward portion of said augmenter tube arranged for the entrance of cooling air into said elongated augmenter tube from said nacelle air inlet, and valve means disposed within the forward portion of said augmenter tube arranged for controlling the admixture. of said cooling air and said exhaust gases within said augmenter tube.

11. An aircraft power plant installation comprising an air cooled engine, an elongated nacelle enclosing said engine, said nacelle having an air inlet at its forward portion for the entrance of' cooling air to the interior of said nacelle, saidnacelle having an outlet at its trailing portion, an elongated augmenter tube having its forward portion in communication with the exhaust gases of said engine, said elongated augmenter tube extending continuously rearwardly to and through said outlet at said nacelle trailing portion, a forwardly directed open ing associated with the forward portion of said augmenter tube/arranged for the entrance of cooling air into said augmenter tube for admixture with said engine exhaust gases there within and the discharge thereof from said augmenter. tube into the airstream through said nacelle outlet, first valve means disposed within the trailing portion of said nacelle for controlling the relative flow of cooling air passing over said engine for the cooling thereof and second valve means disposed within the forward portionv of said augmenter tube for controlling the iiow of cooling air into said augmenter tube.

12. An aircraft power plant installation comprising an air cooled engine, an elongated nacelle enclosing said engine, said nacelle having an air inlet at its forward portion for the entrance of cooling air to the interior of said nacelle, said nacelle having an outlet at its trailing portion, an elongated augmenter tube having its forward portion in communication with the exhaust gases of said engine, said augmenter tube extending rearwardly through said outlet at said nacelle trailing portion, a forwardly directed opening associated with the forward portion of said augmenter tube arranged for the entrance of cooling air into said elongated augmenter tube for admixture with said engine exhaust gases therewithin and the discharge thereof from said augmenter tube into the airstream, through said nacelle outlet, valve means operatively associated with said forwardly directed opening of said augmenter tube arranged for controlling the admixture of said cooling air and said exhaust gases within said augmenter tube, and further valve means operatively mounted within said nacelle exteriorly' of said augmenter tube for controlling the relative flow of cooling air passing over said engine for the cooling thereof;

13..Ihe combination with an aircraft power plant installation having an air cooled engine and a nacelle enclosing said engine, said nacelle having cooling air inlet and outlet openings at its leading and trailing extremities, of an engine exhaust duct co-extensive with the length of said nacelle having an inlet forward of said engine adjacent said nacelle air inlet and an outlet adjacent said air outlet, means for conducting exhaust gases from said engine to said exhaust duct, valve means disposed within said nacelle arranged for the control of the cooling air flow, said valve means being disposed exteriorly of the said exhaust duct, the common air inlets and outlets in both said nacelle and said exhaust duct arranged to admit cooling air to said nacelle for cooling said engine and to said exhaust duct for admixture with said exhaust gases and arranged such that the engine cooling air is accelerated at said common outlet by said admixed engine exhaust gases to augment the thrust of said power plant installation.

RICHARD S. BOUTELLE.

REFERENCES cirnn The following references are of record in the file of this patent:

UNITED STATES PA'IlEIN'IS Number Name Date 1,279,128 Lake -Sept. 1'7, 1918 1,370,197 ,Bolotofr" Mar. 1, 1921 2,048,399 Leaning July 21, 1936 2,177,642 Fellers Oct. 31', 1939 2,390,161 Mercier Dec. 4, 1945 2,401,941 Lee June 11, 1946 OTHER REFERENCES Ser. No. 326,141, Ramshorn (A. P. C.)., published May 11, 19.43. 

